The "Quick Buy" button doesn't work on ebooks.faithlife.com the same way it does on logos.com. On the latter website, it bypasses the shopping cart and buys the book immediately. That's as it should be. But on the former site, it doesn't do anything different than the "Add to Cart" button.
I reported this problem years ago before the website was overhauled, but I can't remember whether it was ever fixed and is now broken again, or whether it's been this way all along including with the new website rewrite. I'm also not sure if it's something that other people aren't seeing, but I can document the behavior as it happens for me every time, no matter what browser I'm using.
Here's a video of it:
https://www.screencast.com/t/1BvLon5Q